8 1/2" would be correct, and hard drives always used removable disc's (about the size of a large pizza). Winchester style disc's were just starting to come out, and after they did, every one had a lot of very large dangerous frisbies laying around.
The old style removable disc's were great for phisical security though....you had a large cannister to carry approx 6 disks with you (heavy though).
Floppies went from 8 1/2 to 5 1/2 to the present 3 1/2. And now we have usb flashdrives that are much more efficient.

[EDIT] We even had one punchcard machine - old at that time- that used a wire node style physical memory (damn, I've forgotten the name of the bloody heavy thing) [EDIT/]